Method and apparatus for measuring the acoustic velocity

Abstract

A portable device for accurately measuring acoustic velocities in solids. This portable hand-held device (100) uses dual receiving transducer tips (110, 112) to allow differential measurement of acoustic velocity in a solid. A body having a handle uses a transmitting transducer tip (108) to transmit acoustic energy to a solid. The first receiving transducer tip (110) is used in conjunction with a second receiving transducer tip (112) mounted on the body a fixed distance from the first (110). The device (100) uses the differences in the time of arrival of the wavefront at the first and second transducers to calculate the acoustic velocity in a given solid. This differential measurement method reduces acoustic velocity measurement inaccuracies.

Having thus described the invention, we claim: 
     
       1. A hand-held portable device for contact measurement of the velocity of sound in a solid comprising: (a) a body having a handle;   (b) a transmitting transducer assembly on the body for converting electrical pulses to a first set of acoustic pulses and transmitting first set of acoustic pulses to the solid;   (c) a first receiving transducer assembly on the body capable of moving along an axis perpendicular to a line formed between the first receiving transducer assembly and the transmitting transducer assembly a first distance from the transmitting transducer assembly for receiving the first set of acoustic pulses transmitted through the solid and converting the first set of acoustic pulses to a first set of electrical pulses;   (d) a second receiving transducer on the body a second distance along a line formed by the transmitting transducer assembly and the first receiving transducer, further removed from the transmitting transducer assembly than is the first receiving transducer assembly for receiving the first set of acoustic pulses transmitted through the solid and converting the first set of acoustic pulses to a second set of electrical pulses; and   thereby enabling measurement of acoustic velocity of the solid by measuring the time of receipt difference between the first and second set of electrical pulses and elimination of the coupling effects on the measurement.   
     
     
       2. The device of claim 1 wherein the transmitting transducer assembly, first receiving transducer assembly, and second receiving transducer assembly are mounted in a straight line. 
     
     
       3. The device of claim 1 wherein the first distance is much less than a path through the body between the transmitting transducer assembly and the receiver transducer assemblies. 
     
     
       4. The device of claim 1 wherein the transmitting and receiving transducer assemblies further comprise piezoelectric crystals. 
     
     
       5. The device of claim 1 wherein the transmitting and receiving transducer assemblies further comprise compression wave generating piezoelectric crystals. 
     
     
       6. The device of claim 1 wherein the transmitting and receiving transducer assemblies further comprise shear wave generating piezoelectric crystals. 
     
     
       7. The device of claim 1 wherein the transmitting and receiving transducer assemblies further comprise shear and compression wave generating piezoelectric crystals. 
     
     
       8. A hand-held portable device for reducing coupling effects in contact measurements of the velocity of sound in a solid comprising: (a) a first arm having a lengthwise axis;   (b) a second arm, shorter than said first arm whose lengthwise axis is substantially parallel to the lengthwise axis of and a first distance from said first arm and connected to said first arm over a small portion of said first arm's length;   (c) a third arm having a lengthwise axis which is substantially parallel to the lengthwise axis of and substantially the same length as the first arm at substantially the same distance from, in opposite direction and in the same plane as the first arm;   (d) a handle connected to said first and third arms suitable for applying a force along lengthwise axes of said first, second and third arms;   (e) a first transducer assembly rigidly attached at an end of the third arm opposite the handle for transmitting acoustic signals into the solid;   (f) a second transducer assembly rigidly attached at an end of the first arm opposite the handle said first distance being much less than an acoustic path along the lengthwise axis of the third arm through the handle and along the lengthwise axis of the first arm, said second transducer assembly capable of moving along said the lengthwise axis of the first arm for receiving the acoustic signals transmitted into the solid; and   (g) a third transducer assembly rigidly attached to the second arm along the lengthwise axis of the second arm, for receiving the acoustic signals transmitted into the solid; thereby allowing the elimination of the effects of coupling between the first transducer and the solid and allowing discrimination between signals passing through the body of the device and those passing through the solid.